The matrix protein gene sequence analysis reveals close relationship between peste des petits ruminants virus (PPRV) and dolphin morbillivirus

Dynamic evolution of peste des petits ruminants virus in sheep and goat hosts across India reveals the swift surge of F gene

Peste des petits ruminants (PPR), an acute febrile viral disease impacting goats and sheep flocks, manifests with pyrexia, mucopurulent nasal and ocular discharges, necrotizing and erosive stomatitis, pneumonia, and enteritis. The disease-instigating agent, PPR virus, pertains to the Morbillivirus caprinae genus in the Paramyxoviridae family. The endemic presence of PPR in India results in notable economic losses due to heightened mortality and morbidity in infected animals. Understanding viral pathogen evolution is pivotal for delineating their emergence in diverse environments. This study explores the molecular evolutionary patterns of PPRV, concentrating on the N and F structural genes isolated from Indian sheep and goats. Analyzing evolutionary rate, phylogenetics, selection pressure, and codon usage bias, we determined the time to the most recent common ancestor (tMRCA) as 1984, 1973, 2000, and 2004 for goat and sheep's N and F genes, respectively, with evolutionary rates ranging from 2.859 x 103 to 4.995 x 104. The F-gene is found to exhibit a faster evolution than the N-gene, indicating apparent virus transmission across the regions of India, as supported by phylogenetic analysis. Codon usage bias examination, incorporating nucleotide composition and various plots (effective number of codon plot, parity plot, neutrality plot), suggests the evolution in India influenced by both natural selection and mutational pressure, resulting in alterations in the virus's codon bias. The integrated analysis underscores the significant role of selection pressures, implying PPRV's co-evolution and adaptations influenced by various genes. Insights from this study can guide effective disease control and vaccine development, aiding in managing PPR outbreaks in India and beyond.

Nucleotide amplification and sequencing of the GC-rich region between matrix and fusion protein genes of peste des petits ruminants virus

Peste des petits ruminants virus (PPRV) causes a highly devastating disease of sheep and goats, that threatens the conservation of small wild ruminants. The development of PPRV vaccines, diagnostics and therapeutics, greatly depends on in-depth genomic data. Yet, high guanine-cytosine (GC) content between matrix (M) and fusion (F) genes of PPRV poses difficulty for both primer design and nucleotide amplification. In turn, this has led into absence or low nucleotide sequence coverage in this region. This poses a risk of missing important part of the genome that could help to infer viral evolution. Here, an overlapping long-read primer-based amplification strategy was developed to amplify the GC-rich fragments between M-F gene junction using nexus gradient polymerase chain reaction (PCR). The resulting amplicons were sequenced by dideoxynucleotide cycle sequencing and compared with other PPRV nucleotide sequences available at GenBank. Our findings indicate clear PCR amplification products with expected size of the GC-rich fragments on agarose gel electrophoresis. The sequencing results of these fragments indicate 99.5 % nucleotide identity with PPRV strain KY628761. An extremely difficult PCR target of 67.4 % GC contents was successfully amplified and sequenced using this long-read primer approach. The long-read primer set may be used in tiling multiplex PCR for complete genome sequencing of PPRV.

Molecular insights into peste des petits ruminants virus identified in Bangladesh between 2008 and 2020

An in-depth knowledge of the molecular evolution of the peste des petits ruminants virus (PPRV) is critical for the success of the current global eradication program. For this reason, a molecular evolutionary analysis of PPRVs circulating in Bangladesh over a decade (2008-2020) was performed. The complete genome sequencing of three PPRV isolates from 2008 (BD2), 2015 (BD12) and 2017 (BD17) as well as full length nucleocapsid (N), matrix (M) and fusion (F) gene sequencing of seven more samples from 2015 to 2020 was performed. Phylogenetic analysis classified all ten PPRVs from Bangladesh as members of lineage IV and showed that they were closely related to PPRV strains detected in China and Tibet during 2007-2008, and India during 2014-2018. Time scale Bayesian Maximum Clade Credibility (MCC) phylogenetic analysis of the three complete genomes revealed a mean Time to Most Recent Common Ancestor (TMRCA) of 2000. Comparative deduced amino acid residue analysis at various functional motifs of PPRVs related to virus structure and function, virulence and host adaptation, receptor binding sites and polymerase activity revealed conserved residues among the PPRVs from Bangladesh. In total sixteen epitopes were predicted from four immunogenic proteins i.e. N, M, F and haemagglutinin (H). Interestingly, the predicted epitopes from the N and M proteins shared conserved epitopes with two vaccine strains currently being used, indicating that the strains from Bangladesh could be potentially used as alternative local vaccines.

Virus-Like Particles Derived From a Virulent Strain of Pest des Petits Ruminants Virus Elicit a More Vigorous Immune Response in Mice and Small Ruminants Than Those From a Vaccine Strain

Peste des petits ruminants (PPRs) is highly contagious, acute or subacute disease of small ruminants caused by peste des petits ruminants virus (PPRV). To date, several studies have designed and evaluated PPRV-like particles (VLPs) as a vaccine candidate for the prevention and control of PPR, with the majority of these VLPs constructed using sequences derived from a PPRV vaccine strain due to its high immunogenicity. However, because of the lack of available genetic material and certain structural proteins and/or the alteration of posttranslational glycosylation modifications, the immunogenicity of VLPs derived from a vaccine strain is not always optimal. In this study, two PPRV VLP candidates, derived from either the lineage IV Tibet/30 virulent strain or the lineage II Nigeria 75/1 vaccine strain, were generated using a baculovirus system through the coexpression of the PPRV matrix (M), hemagglutinin (H), and fusion (F) proteins in the high expression level cell line High Five. These VLPs were then used to immunize mice, goats, and sheep followed by two boosts after primary immunization. Both VLPs were found to induce a potent humoral immune response as demonstrated by the high ratio of immunoglobulin G1 (IgG1) to IgG2a. In all animals, both VLPs induced high titers of virus-neutralizing antibodies (VNAs), as well as H- and F-specific antibodies, with the Tibet/30 VLPs yielding higher antibody titers by comparison to the Nigeria 75/1 VLPs. Studies in mice also demonstrated that the Tibet/30 VLPs induced a more robust interleukin 4 and interferon γ response than the Nigeria 75/1 VLPs. Goats and sheep immunized with both VLPs exhibited a robust humoral and cell-mediated immune response. Furthermore, our results demonstrated that the VLPs derived from the virulent lineage IV Tibet/30 strain were more immunogenic, inducing a more potent and robust humoral and cell-mediated immune response in vaccinated animals by comparison to the lineage II Nigeria 75/1 vaccine strain VLPs. In addition, VNA titers were significantly higher among animals vaccinated with the Tibet/30 VLPs by comparison to the Nigeria 75/1 VLPs. Taken together, these findings suggest that VLPs derived from the virulent lineage IV Tibet/30 strain are more immunogenic by comparison to those derived from the lineage II Nigeria 75/1 vaccine strain and thus represent a promising vaccine candidate for the control and eradication of PPR.

Development of vaccines for prevention of peste-des-petits-ruminants virus infection

Peste des petits ruminants (PPR) is a highly contagious and fatal disease of small ruminants, particularly sheep and goats. This disease leads to high morbidity and mortality of small ruminants, thus resulting in devastating economic loss to the livestock industry globally. The severe disease impact has prompted the Food and Agriculture Organization of the United Nations (FAO) and the World Organization for Animal Health (OIE) to develop a global strategy for the control and eradication of PPR by 2030. Over the past decades, the control of PPR is mainly achieved through vaccinating the animals with live-attenuated vaccines, e.g., rinderpest vaccines. As a closely related disease to PPR of large ruminants, rinderpest was eradicated in 2011 and its vaccines subsequently got banned in order to keep rinderpest-free zones. Consequently, it is desirable to develop homologous PPR vaccines to control the disease. The present review summarizes the objectives of PPR control and eradication by focusing on the homologous PPR vaccines.

Immunoinformatics Approach for Multiepitope Vaccine Prediction from H, M, F, and N Proteins of Peste des Petits Ruminants Virus

Background

Small ruminant morbillivirus or peste des petits ruminants virus (PPRV) is an acute and highly contagious viral disease of goats, sheep, and other livestock. This study aimed at predicting an effective multiepitope vaccine against PPRV from the immunogenic proteins haemagglutinin (H), matrix (M), fusion (F), and nucleoprotein (N) using immunoinformatics tools.

Materials and Methods

The sequences of the immunogenic proteins were retrieved from GenBank of the National Center for Biotechnology Information (NCBI). BioEdit software was used to align each protein from the retrieved sequences for conservancy. Immune Epitope Database (IEDB) analysis resources were used to predict B and T cell epitopes. For B cells, the criteria for electing epitopes depend on the epitope linearity, surface accessibility, and antigenicity.

Results

Nine epitopes from the H protein, eight epitopes from the M protein, and ten epitopes from each of the F and N proteins were predicted as linear epitopes. The surface accessibility method proposed seven surface epitopes from each of the H and F proteins in addition to six and four epitopes from the M and N proteins, respectively. For antigenicity, only two epitopes ₁₄₂PPERV₁₄₆ and ₆₃DPLSP₆₇ were predicted as antigenic from H and M, respectively. For T cells, MHC-I binding prediction tools showed multiple epitopes that interacted strongly with BoLA alleles. For instance, the epitope ₄₅MFLSLIGLL₅₃ from the H protein interacted with four BoLA alleles, while ₂₇₆FKKILCYPL₂₈₄ predicted from the M protein interacted with two alleles. Although F and N proteins demonstrated no favorable interaction with B cells, they strongly interacted with T cells. For instance, ₃₅₈STKSCARTL₃₆₆ from the F protein interacted with five alleles, followed by ₃₄₀SQNALYPMS₃₄₈ and ₄₄₂IDLGPAISL₄₅₀ that interacted with three alleles each. The epitopes from the N protein displayed strong interaction with BoLA alleles such as ₄₉₀RSAEALFRL₄₉₈ that interacted with five alleles, followed by two epitopes ₂ATLLKSLAL₁₀ and ₃₀₄QQLGEVAPY₃₁₂ that interacted with four alleles each. In addition to that, four epitopes ₃TLLKSLALF₁₁, ₃₅₆YFDPAYFRL₃₆₄, ₃₆₀AYFRLGQEM₃₆₈, and ₄₁₂PRQAQVSFL₄₂₀ interacted with three alleles each.

Conclusion

Fourteen epitopes were predicted as promising vaccine candidates against PPRV from four immunogenic proteins. These epitopes should be validated experimentally through in vitro and in vivo studies.

Peste des Petits Ruminants Virus-Like Particles Induce a Potent Humoral and Cellular Immune Response in Goats

Peste des petits ruminants is a highly contagious acute or subacute disease of small ruminants caused by the peste des petits ruminants virus (PPRV), and it is responsible for significant economic losses in animal husbandry. Vaccination represents the most effective means of controlling this disease, with virus-like particle (VLP) vaccines offering promising vaccine candidates. In this study, a PPRV VLP-based vaccine was developed using a baculovirus expression system, allowing for the simultaneous expression of the PPRV matrix (M), hemagglutinin (H), fusion (F) and nucleocapsid (N) proteins in insect cells. Immunization of mice and goats with PPRV VLPs elicited a robust neutralization response and a potent cellular immune response. Mouse studies demonstrated that VLPs induced a more robust IFN-γ response in CD4⁺ and CD8⁺ T cells than PPRV Nigeria 75/1 and recruited and/or activated more B cells and dendritic cells in inguinal lymph nodes. In addition, PPRV VLPs induced a strong Th1 class response in mice, as indicated by a high IgG2a to IgG1 ratio. Goat studies demonstrated that PPRV VLPs can induce the production of antibodies specific for F and H proteins and can also stimulate the production of virus neutralizing antibodies to the same magnitude as the PPRV Nigeria 75/1 vaccine. Higher amounts of IFN-γ in VLP-immunized animal serum suggested that VLPs also elicited a cellular immune response in goats. These results demonstrated that VLPs elicit a potent immune response against PPRV infection in small ruminants, making PPRV VLPs a potential candidate for PPRV vaccine development.

New world origin of canine distemper: Interdisciplinary insights

OBJECTIVE

Canine distemper virus (CDV), human measles virus (HMV), and rinderpest virus (RPV) of cattle are morbilliviruses that have caused devastating outbreaks for centuries. This paper seeks to reconstruct the evolutionary history of CDV.

MATERIALS AND METHODS

An interdisciplinary approach is adopted, synthesizing paleopathological analysis of 96 Pre-Columbian dogs (750-1470 CE) from the Weyanoke Old Town, Virginia site, with historical reports, molecular analysis and morbilliviral epidemiology.

RESULTS

Both measles (c.900CE) and rinderpest (c. 376 BCE) were first reported in Eurasia, while canine distemper was initially described in South America much later (1735 CE); there are no paleopathological indications of CDV in Weyanoke Old Town dogs. Molecularly, CDV is closely related to HMV, while viral codon usage indicates CDV may have previously infected humans; South American measles epidemics occurred prior to the emergence of canine distemper and would have facilitated HMV transmission and adaptation to dogs.

CONCLUSIONS

The measles epidemics that decimated indigenous South American populations in the 1500-1700 s likely facilitated the establishment of CDV as a canine pathogen, which eventually spread to Europe and beyond.

SIGNIFICANCE

Understanding the historical and environmental conditions that have driven morbilliviral evolution provides important insights into potential future threats of animal/human cross-species infections.

LIMITATIONS

Interpreting historical disease descriptions is difficult and the archaeological specimens are limited. Molecular sequence data and codon usage analyses rely on modern viruses.

SUGGESTIONS FOR FURTHER RESEARCH

Interdisciplinary approaches are increasingly needed to understand diseases of the past and present, as critical information and knowledge is scattered in different disciplines.

Analyses of nucleotide, codon and amino acids usages between peste des petits ruminants virus and rinderpest virus

Peste des petits ruminants virus (PPRV) and rinderpest virus (RPV) are two causative agents of an economically important disease for ruminants (i.e., sheep, cattle and goat). In this study, the nucleotide, codon and amino acid usages for PPRV and RPV have been analyzed by multivariate statistical methods. Relative synonymous codon usage (RSCU) analysis represents that ACG for Thr and GCG for Ala are selected with under-representation in both PPRV and RPV, and AGA for Arg in PPRV and AGG for Arg in RPV are used with over-representation. The usage of nucleotide pair (CpG) tends to be removed from viral genes of the two viruses, suggesting that other evolutionary forces take part in evolutionary processes for viral genes in addition to mutation pressure from nucleotide usage at the third codon position. The overall nucleotide usage of viral gene is not major factor in shaping synonymous codon usage patterns, while the nucleotide usages at the third codon position and the nucleotide pairs play important roles in shaping synonymous codon usage patterns. Although PPRV and RPV are closely related antigenically, the codon and amino acid usage patterns for viral genes represent a significant genetic diversity between PPRV and RPV. Moreover, the overall codon usage trends for viral genes between PPRV and RPV are mainly influenced by mutation pressure from nucleotide usage at the third codon position and translation selection from hosts. Taken together, this is first comprehensive analyses for nucleotide, codon and amino acid usages of viral genes of PPRV and RPV and the findings are expected to increase our understanding of evolutionary forces influencing viral evolutionary pathway and adaptation toward hosts.

Peste des petits ruminants virus infection of small ruminants: a comprehensive review

Peste des petits ruminants (PPR) is caused by a Morbillivirus that belongs to the family Paramyxoviridae. PPR is an acute, highly contagious and fatal disease primarily affecting goats and sheep, whereas cattle undergo sub-clinical infection. With morbidity and mortality rates that can be as high as 90%, PPR is classified as an OIE (Office International des Epizooties)-listed disease. Considering the importance of sheep and goats in the livelihood of the poor and marginal farmers in Africa and South Asia, PPR is an important concern for food security and poverty alleviation. PPR virus (PPRV) and rinderpest virus (RPV) are closely related Morbilliviruses. Rinderpest has been globally eradicated by mass vaccination. Though a live attenuated vaccine is available against PPR for immunoprophylaxis, due to its instability in subtropical climate (thermo-sensitivity), unavailability of required doses and insufficient coverage (herd immunity), the disease control program has not been a great success. Further, emerging evidence of poor cross neutralization between vaccine strain and PPRV strains currently circulating in the field has raised concerns about the protective efficacy of the existing PPR vaccines. This review summarizes the recent advancement in PPRV replication, its pathogenesis, immune response to vaccine and disease control. Attempts have also been made to highlight the current trends in understanding the host susceptibility and resistance to PPR.

Diagnosis and control of peste des petits ruminants: a comprehensive review

Peste des petits ruminants (PPR) is an acute, highly contagious, world organization for animal health (OIE) notifiable and economically important transboundary viral disease of sheep and goats associated with high morbidity and mortality and caused by PPR virus. PPR is considered as one of the main constraints in augmenting the productivity of small ruminants in developing countries and particularly severely affects poor farmer's economy. The disease is clinically manifested by pyrexia, oculo-nasal discharges, necrotizing and erosive stomatitis, gastroenteritis, diarrhoea and bronchopneumonia. The disease can be diagnosed from its clinical signs, pathological lesions, and specific detection of virus antigen/antibodies/genome in the clinical samples by various serological tests and molecular assays. PPR is the one of the priority animal diseases whose control is considered important for poverty alleviation in enzootic countries. Availability of effective and safe live attenuated cell culture PPR vaccines and diagnostics have boosted the recently launched centrally sponsored control programme in India and also in other countries. This review article primarily focus on the current scenario of PPR diagnosis and its control programme with advancement of research areas that have taken place in the recent years with future perspectives.

A simple model explains the dynamics of preferential host switching among mammal RNA viruses

A growing number of studies support a tendency toward preferential host switching, by parasites and pathogens, over relatively short phylogenetic distances. This suggests that a host switch is more probable if a potential host is closely related to the original host than if it is a more distant relative. However, despite its importance for the health of humans, livestock, and wildlife, the detailed dynamics of preferential host switching have, so far, been little studied. We present an empirical test of two theoretical models of preferential host switching, using observed phylogenetic distributions of host species for RNA viruses of three mammal orders (primates, carnivores, and ungulates). The analysis focuses on multihost RNA virus species, because their presence on multiple hosts and their estimated ages of origin indicate recent host switching. Approximate Bayesian computation was used to compare observed phylogenetic distances between hosts with those simulated under the theoretical models. The results support a decreasing sigmoidal model of preferential host switching, with a strong effect from increasing phylogenetic distance, on all three studied host phylogenies. This suggests that the dynamics of host switching are fundamentally similar for RNA viruses of different mammal orders and, potentially, a wider range of coevolutionary systems.

Sequence and phylogenetic analyses of the structural genes of virulent isolates and vaccine strains of peste des petits ruminants virus from India

Peste des petits ruminants (PPR) is an acute, highly contagious, notifiable and economically important transboundary viral disease of sheep and goats. In this study, sequence and phylogenetic analyses of structural protein genes, namely the nucleocapsid (N), the matrix (M), the fusion (F) and the haemagglutinin (H) coding sequences of virulent and vaccine strains of PPR virus (PPRV), were undertaken to determine the genetic variations between field isolates and vaccine strains. The open reading frame (ORF) of these genes of the isolates/strains was amplified by RT-PCR, cloned and sequenced. The ORF of N, M, F and H genes was 1578, 1008, 1641 and 1830 nucleotides (nt) in length and encodes polypeptides of 525, 335, 546 and 609 amino acids (aa), respectively, as reported earlier. Comparative sequence analyses of these four genes of isolates/strains were carried out with published sequences. It revealed an identity of 97.7-100% and 97.7-99.8% among the Asian lineage IV and 89.6-98.7% and 89.8-98.9% with other lineages of PPRV at nt and aa levels, respectively. The phylogenetic analyses of these isolates based on the aa sequences showed that all the viruses belonged to lineage IV along with other Asian isolates. This is in agreement with earlier observations that only PPRV lineage IV is in circulation in India since the disease was first reported. Further, sequence analysis of the thermostable/thermo-adapted vaccine strains showed no significant changes in the functional or structural surface protein-coding gene sequences. It is important to monitor the circulation of the PPRV in susceptible animals by H gene-based sequence comparisons in addition to the F gene- and N gene-based approaches to identify the distribution and spread of virus in the regular outbreaks that occur in endemic countries like India.

Full genome sequences of two virulent strains of peste-des-petits ruminants virus, the Côte d'Ivoire 1989 and Nigeria 1976 strains

Peste-des-petits ruminants virus (PPRV) causes acute febrile illness in both farmed and wild small ruminants, with associated mortality rates of 50-80%. PPRV is a member of the Morbillivirus genus within the Paramyxovirus family and although there are many full length genome sequences available for members of this family, their availability for PPRV in particular is limited. We have determined the full length sequences representing two virulent strains of PPRV, the Côte d'Ivoire 1989 (CI/89) and Nigeria 1976 (Ng76/1) strains. We present an alignment of the promoter regions of these viruses with other available PPRV promoter sequences and have identified domains in PPRV proteins believed to be critical for paramyxovirus promoter attenuation. We have also analysed the proteins of these viruses, comparing them to other available PPRV protein sequences and identified motifs that were previously recognised as being required for the function of other paramyxovirus proteins.

Sequence of the nucleocapsid gene and genome and antigenome promoters for an isolate of porpoise morbillivirus

We have determined the first complete sequence of the nucleocapsid (N) gene of the porpoise morbillivirus (PMV) as well as the genome leader and trailer sequences which encode the genome and antigenome promoters, respectively. The PMV N gene is 1686 nucleotides long with a single open reading frame (ORF) encoding a protein of 523 amino acids with a predicted molecular weight of 57.39kDa. The nucleotide sequence of the N gene shows the closest identity (89%) to that of another cetacean morbillivirus, dolphin morbillivirus (DMV). Lower degrees of identity were found with the other members of the morbilliviruses genus; 67% identity to PDV and RPV, 68% to PPRV, 69% to CDV and 70% to MV. The distance from the 3' end of the genome up to the start of the N ORF is 107 nucleotides, identical to that found in all other morbilliviruses, and encompasses the genome promoter (GP) sequence. This promoter shows the same regions of conservation as found in other morbilliviruses with repeated CXXXXX motifs at positions 79-84, 85-90, and 91-96, the same bi-partite promoter arrangement found in many paramyxoviruses. The antigenome promoter (AGP) shows a similar arrangement, indicating a high degree of conservation in these functionally important regions.

Sequence analysis of the nucleoprotein gene of Asian lineage peste des petits ruminants vaccine virus

The complete nucleotide sequence of the nucleocapsid (N) protein of the peste-des-petits ruminants vaccine virus (PPRV Sungri/96) belonging to the Asian lineage was determined. The gene was 1692 nucleotides in length and encoded a polypeptide of 525 amino acids. The PPRV Sungri/96 N gene has a nucleotide homology of 92% for PPRV Nigeria 75/1 to 55.5% for canine distemper virus. At amino acid level the homology was 94.1% with PPRV Nigeria 75/1, while with other morbilliviruses, PPRV Sungri/96 had only 71.4-64.9% amino acid identity. The phosphorylation prediction reveals eight conserved sites across morbilliviruses, whereas in the C-terminal portion of the protein the sites are not conserved. Phylogenetic analysis of different N proteins of morbilliviruses revealed five well-defined clusters as observed previously. To the best of our knowledge this is the first report describing the nucleocapsid gene sequence of PPRV Indian isolate.

Involvement of morbilliviruses in the pathogenesis of demyelinating disease

Two members of the morbillivirus genus of the family Paramyxoviridae, canine distemper virus (CDV) and measles virus (MV), are well-known for their ability to cause a chronic demyelinating disease of the CNS in their natural hosts, dogs and humans, respectively. Both viruses have been studied for their potential involvement in the neuropathogenesis of the human demyelinating disease multiple sclerosis (MS). Recently, three new members of the morbillivirus genus, phocine distemper virus (PDV), porpoise morbillivirus (PMV) and dolphin morbillivirus (DMV), have been discovered. These viruses have also been shown to induce multifocal demyelinating disease in infected animals. This review focuses on morbillivirus-induced neuropathologies with emphasis on aetiopathogenesis of CNS demyelination. The possible involvement of a morbillivirus in the pathogenesis of multiple sclerosis is discussed.

One-step multiplex RT-PCR assay for the detection of peste des petits ruminants virus in clinical samples

A single-tube one-step multiplex RT-PCR was standardized to amplify both 337 bp and 191 bp fragments of N and M genes of peste des petits ruminants virus (PPRV), respectively, and only a 337 bp fragment of N gene of Rinderpest virus (RPV). The RT-PCR using purified viral RNA was easily adopted for direct detection of PPRV in clinical field samples and its differentiation from RPV. The amplified N and M gene products were confirmed to be PPRV- and RPV-specific by their size in 1.5% agarose gel and restriction analysis. In the assay, the Qiagen one-step RT-PCR kit containing the Ominiscript and Sensiscript reverse transcriptases and Hot star Taq DNA polymerase was utilized. The sensitivity of the assay was found to be 100 fg of PPRV RNA. Compared with a two-step assay, the one-step assay is easier and time-saving as it requires just a single buffer for both reactions, reverse transcription (RT) and PCR. In experimentally infected goats, PPRV was detectable by the one-step RT-PCR in nasal and ocular swabs 7-17 days post infection (p.i.). and in oral swabs 7-15 days p.i. Out of 32 clinical field samples tested, 18 were positive by sandwich ELISA (S-ELISA), while 22 were positive by the one-step RT-PCR.

Matrix protein and glycoproteins F and H of Peste-des-petits-ruminants virus function better as a homologous complex

The matrix (M) protein of paramyxoviruses forms an inner coat to the viral envelope and serves as a bridge between the surface glycoproteins (F and H) and the ribonucleoprotein core. Previously, a marker vaccine (RPV-PPRFH) was produced for the control of peste des petits ruminants (PPR) disease, where the F and H genes of Rinderpest virus (RPV) were replaced with the equivalent genes from Peste-des-petits-ruminants virus (PPRV); however, this virus grew poorly in tissue culture. The poor growth of the RPV-PPRFH chimeric virus was thought to be due to non-homologous interaction of the surface glycoproteins with the internal components of the virus, in particular with the M protein. In contrast, replacement of the M gene of RPV with that from PPRV did not have an effect on the viability or replication efficiency of the recombinant virus. Therefore, in an effort to improve the growth of the RPV-PPRFH virus, a triple chimera (RPV-PPRMFH) was made, where the M, F and H genes of RPV were replaced with those from PPRV. As expected, the growth of the triple chimera was improved; it grew to a titre as high as that of the unmodified PPRV, although comparatively lower than that of the parental RPV virus. Goats infected with the triple chimera showed no adverse reaction and were protected from subsequent challenge with wild-type PPRV. The neutralizing-antibody titre on the day of challenge was approximately 17 times higher than that in the RPV-PPRFH group, indicating RPV-PPRMFH as a promising marker-vaccine candidate.

Sequence analysis of the haemagglutinin and fusion protein genes of peste-des-petits ruminants vaccine virus of Indian origin

The amino acid composition of the two surface proteins of peste-des-petits ruminants vaccine virus belonging to lineage four from India were deduced from the nucleotide sequence. The fusion (F) protein gene of PPRV Sungri/96 is 2405 nucleotides long and in relation to the length, it is 80 nucleotides longer than that of PPRV Nigeria/75/1 which are found to be present at the 5'UTR of this virus. The complete F gene alignment with other morbillivirus reveals a homology of 89% with PPRV/Nigeria/75/1 and 48-51% with other morbilliviruses. The F protein of PPRV Sungri/96 exhibited characteristics similarity to those of other morbillivirus F proteins. The overall amino acid similarity with its counterpart PPRV Nigeria/75/1 was 96%; with other morbilliviruses it is 65-74%. The PPRV Sungri/96 haemagglutinin (H) protein gene is 1954 nucleotides long and showed a sequence homology of 90.7% with PPRV/Nigeria/75/1 and with other morbilliviruses it ranged from 33% to 45%. At amino acids level, PPRV Sungri/96 showed a homology of 92.3% with PPRV/Nigeria/75/1 and 34-49% with other morbilliviruses. The phylogenetic tree constructed for F and H gene reveals four separate groups which is very similar to that found in other genes. To the best of our knowledge this is the first report describing the F and H genes of an Indian isolate.

Long untranslated regions of the measles virus M and F genes control virus replication and cytopathogenicity

Measles is still a major cause of mortality mainly in developing countries. The causative agent, measles virus (MeV), is an enveloped virus having a nonsegmented negative-sense RNA genome, and belongs to the genus Morbillivirus of the family Paramyxoviridae. One feature of the moribillivirus genomes is that the M and F genes have long untranslated regions (UTRs). The M and F mRNAs of MeV have 426-nucleotide-long 3' and 583-nucleotide-long 5' UTRs, respectively. Though these long UTRs occupy as much as approximately 6.4% of the virus genome, their function remains unknown. To elucidate the role of the long UTRs in the context of virus infection, we used the reverse genetics based on the virulent strain of MeV, and generated a series of recombinant viruses having alterations or deletions in the long UTRs. Our results showed that these long UTRs per se were not essential for MeV replication, but that they regulated MeV replication and cytopathogenicity by modulating the productions of the M and F proteins. The long 3' UTR of the M mRNA was shown to have the ability to increase the M protein production, promoting virus replication. On the other hand, the long 5' UTR of the F mRNA was found to possess the capacity to decrease the F protein production, inhibiting virus replication and yet greatly reducing cytopathogenicity. We speculate that the reduction in cytopathogenicity may be advantageous for MeV fitness and survival in nature.

Analysis of the matrix protein gene sequence of the Asian lineage of peste-des-petits ruminants vaccine virus

The M gene nucleotide sequence of an Indian peste-des-petits ruminants (PPRV) vaccine virus ("PPRV Sungri/96") belonging to Asian lineage was determined. The gene is 1476 nucleotides long with a single open reading frame (ORF). The nucleotide and predicted amino acid sequence was compared with the homologous region of the African Lineage Vaccine virus "PPRV/Nigeria/75/1". The nucleotide sequence of the "PPRV Sungri/96" was 86% identical to that of "PPRV/Nigeria/75/1", while a homology of 93% and 95% could be observed in the ORF and amino acids level, respectively. The M gene encodes a protein of 335 amino acids, with a predicted molecular weight (MW) of 37.8 kDa. The ORF is flanked by a 3' untranslated region of 436 nucleotides and a high level of sequence divergence (approximately 30%) could be observed in this region between the vaccine viruses of Asian and African lineages. A high degree of conservation of several amino acids of this protein observed previously was also confirmed in this study.

Comparative nucleotide sequence analysis of the phosphoprotein gene of peste des petits ruminants vaccine virus of Indian origin

The nucleotide sequences of the phosphoprotein (P) gene of peste des petits ruminants (PPRV) vaccine virus (PPRV Sungri/96) belongs to Asian lineage have been determined and the deduced amino acid sequences were compared with another vaccine strain PPRV/Nigeria75/1 and with those of the other morbilliviruses. The 1652 nucleotides of the P gene encode a phosphoprotein of 509 amino acid residues (from nucleotide numbers 60 to 1587), which is 91% identical to that of PPRV/Nigeria75/1. The C protein consists of 177 amino acid residues and is 91% identical with that of PPRV/Nigeria75/1. The conserved mRNA editing site (5'TTAAAAGGGCACAG) was present at positions 742-756 in the P gene, which is conserved in all other morbilliviruses. The CTT trinucleotide sequence is present at the N/P and P/M intergenic region, which is totally conserved in morbilliviruses. This will be the third sequence for the P gene of PPRV since that of the vaccine strain and a wild-type Turkish isolate has been published already.

Comparative sequence analysis of the large polymerase protein (L) gene of peste-des-petits ruminants (PPR) vaccine virus of Indian origin

The complete nucleotide sequence of the large polymerase (L) protein of the peste-des-petits ruminants (PPR) vaccine virus (PPRV Sungri/96) belonging to the Asian lineage was determined. The gene was 6643 nucleotides in length from the gene-start to the gene-end and encoded a polypeptide of 2183 amino acids. The PPRV Sungri/96 has a nucleotide homology of 94.1% for PPRV Nigeria 75/1 to 64.4% for Canine distemper virus. At amino acid level PPRV Sungri/96 has an amino acid identity of 96.2% with PPRV Nigeria 75/1 and 70.4% to 74.8% with other morbilliviruses. All the established domains in L protein characteristic of paramyxoviruses were also found to be present in PPRV Sungri/96. Phylogenetic analysis of different L proteins of morbilliviruses revealed five well-defined clusters as observed previously. The 3' trailer sequence of PPRV Sungri/96 is of 37 nucleotides long which is very similar to that of other morbilliviruses. To the best of our knowledge this is the first report describing the polymerase gene sequence of PPRV Indian isolate.

Full genome sequence of peste des petits ruminants virus, a member of the Morbillivirus genus

Peste des petits ruminants virus (PPRV) causes an acute febrile illness in small ruminant species, mostly sheep and goats. PPRV is a member of the Morbillivirus genus which includes measles, rinderpest (cattle plague), canine distemper, phocine distemper and the morbilliviruses found in whales, porpoises and dolphins. Full length genome sequences for these morbilliviruses are available and reverse genetic rescue systems have been developed for the viruses of terrestrial mammals, with the exception of PPRV. This paper presents the first published full length genome sequence for PPRV. The genome was found to be consistent with the rule-of-six and open reading frames (ORFs) were identified that encoded the eight proteins characteristic of morbilliviruses. At the nucleotide (nt) level, the full length genome of PPRV was most similar to that of rinderpest, the other ruminant morbillivirus. However, at the protein level five of the six structural proteins and the V protein showed a greater similarity to the dolphin morbillivirus (DMV) while only the C and L proteins showed a high relationship to rinderpest.

An insight into the epidemiology of dolphin morbillivirus worldwide

Serum samples from 288 cetaceans representing 25 species and originating from 11 different countries were collected between 1995 and 1999 and examined for the presence of dolphin morbillivirus (DMV)-specific antibodies by an indirect ELISA (iELISA) (N = 267) or a plaque reduction assay (N = 21). A total of 35 odontocetes were seropositive: three harbour porpoises (Phocoena phocoena) and a common dolphin (Delphinus delphis) from the Northeastern (NE) Atlantic, a bottlenose dolphin (Tursiops truncatus) from Kent (England), three striped dolphins (Stenella coeruleoalba), two Risso's dolphins (Grampus griseus) and a bottlenose dolphin from the Mediterranean Sea, one common dolphin from the Southwest (SW) Indian Ocean, three Fraser's dolphins (Lagenodelphis hosei) from the SW Atlantic, 18 long-finned pilot whales (Globicephala melas) and a bottlenose dolphin from the SW Pacific as well as a captive bottlenose dolphin (Tursiops aduncus) originally from Taiwan. The presence of morbillivirus antibodies in 17 of these animals was further examined in other iELISAs and virus neutralization tests. Our results indicate that DMV infects cetaceans worldwide. This is the first report of DMV-seropositive animals from the SW Indian, SW Atlantic and West Pacific Oceans. Prevalence of DMV-seropositives was 85.7% in 21 pilot whales from the SW Pacific and both sexually mature and immature individuals were infected. This indicates that DMV is endemic in these animals. The same situation may occur among Fraser's dolphins from the SW Atlantic. The prevalence of DMV-seropositives was 5.26% and 5.36% in 19 common dolphins and 56 harbour porpoise from the NE Atlantic, respectively, and 18.75% in 16 striped dolphins from the Mediterranean. Prevalence varied significantly with sexual maturity in harbour porpoises and striped dolphins; all DMV-seropositives being mature animals. The prevalence of seropositive harbour porpoise and striped dolphins appeared to have decreased since previous studies. These data suggest that DMV is not endemic within these populations, that they are losing their humoral immunity against the virus and that they may be vulnerable to new epidemics.